Among common absorbent articles such as urine pads, pull-on-type diapers, and tape-on-briefs-type diapers, absorbent articles including a plurality of absorbers stacked in the thickness direction have been devised in an attempt to increase the amount of urine absorbed while minimizing leakage of urine.
In particular, pull-on-type diapers, which are often used by wearers who can walk, may have problems such as twisting and deformation of absorbing cores stacked in the thickness direction during wearing.
As disclosed in Japanese Patent Application Publications Nos. 2009-160242 and 2007-44124, a technique has so far been developed and used in which absorbing cores including a liquid-holding material covered on the top surface, side surfaces, and both sides of the bottom surface, or in its entirety, with a non-woven cloth are stacked in the thickness direction and are bonded together with an adhesive to prevent deformation due to twisting of the absorbing cores and to increase the absorption rate.
However, when the entire liquid-holding material is covered with a non-woven cloth formed of a synthetic fiber, a hydrophilic agent needs to be applied to the non-woven cloth so that it has hydrophilic properties. The hydrophilic agent, however, may be washed away after permeation of urine multiple times, and accordingly the non-woven cloth may lose its hydrophilic properties. It has been reported that, after urination in small amounts multiple times, urine is repelled by the non-woven cloth covering the absorber and leaks from the side surfaces of the absorbing core along the surface of the non-woven cloth.
As disclosed in Japanese Patent Application Publication No. 2006-167196, an attempt has been made to provide a second sheet between an upper absorbing core cut in a U-shape and a lower absorbing core at the central position in the width direction of the absorbing cores for improved diffusibility, which is intended to reduce wetback by effectively utilizing the absorbing cores. However, because of the property of absorbing urine over a wide area of the second sheet, some urine remains on the second sheet after urination multiple times, which makes it difficult to improve the absorption rate.